A pipeline is frequently in the form of an inner liquid carrying pipe disposed within a rigid outer casing. The outer casing isolates the inner pipe from the elements as well as from ground movement and the structural stresses associated therewith. One or more carrier pipes may be disposed within the outer casing, where the inner carrier pipe(s) may be a water or sewer main. An outer casing is frequently positioned about an inner carrier pipe where the carrier pipe crosses a highway or railroad tracks. The outer casing serves to maintain carrier pipe alignment, restrain the carrier pipe against flotation or other movement, and maintain the carrier pipe in fixed position and orientation, such as per grade requirements in the case of a gravity sewer. One or more spacers are typically disposed about the carrier pipe(s) and between the carrier pipe(s) and the outer casing to maintain stationary positioning and fixed spacing of the carrier pipe(s) relative to the outer casing.
Connections between adjacent pipe sections are frequently disposed within an outer casing, particularly where long pipe runs are involved. These pipe connections must also be maintained in fixed position within, and spaced relation from, the outer pipe casing. While the connection between coupled carrier pipes disposed with an outer casing is subject to reduced environmental factors and external forces because of the surrounding outer casing, it is still of critical importance to provide a high strength, secure connection between adjacent pipe sections because of the critical service being provided by the pipeline and because the outer casing makes it more difficult to locate and repair leaks.
Various types of pipe junction holders are available for preventing a pair of joined pipes from becoming disengaged such as when a very large pressure is abruptly applied in the axial direction by a liquid within the pipes. These types of pipe junction holders typically include an annular body having plural through holes each with internal threads. The through holes are aligned radially with the connected pipe sections and bolts inserted into these through holes are tightened so that each bolt engages the outer surface of a pipe section. A push member is frequently disposed between the inner end of the threaded shank of a bolt and the outer peripheral surface of a pipe on which the pipe junction holder is mounted. A roughened, anti-sliding surface may be provided for on an inner portion of the push member so as to frictionally engage the outer surface of the pipe. Tightening of the bolts urges each of the push members into intimate contact with the outer surface of the pipe in connecting the annular body to adjacent ends of the coupled pipes. One example of this type of pipe junction holder is the subject of U.S. Pat. No. 4,092,036, issued on May 30, 1978.
Installing a pipe junction holder connecting in an end-to-end manner carrier pipes in an outer casing is difficult, time consuming and can result in breakage or damage to the sealed pipe connection. Moreover, casing spacers are located intermediate the pipe joint connections and thus do not provide optimal support for the heaviest portions of the carrier pipe network where adjacent carrier pipe sections are connected together. In addition, the reduced support available at the pipe junction holders also destabilizes these connections and renders them more susceptible to leakage caused by vibration and movement as well as from sudden increases in pressure imparted in the axial direction to the internal surface of the joined pipes. This less than optimal support for the pipe connections results in a higher rate of joint failure and leakage which requires removal of both pipe sections and the pipe joint connection from the outer casing for repair with great difficulty and substantial expense.
To date, there is no known pipe coupling arrangement which is also capable of maintaining the connected pipes in fixed position within, and spaced relation from, an outer casing enclosing the connected pipes. The present invention addresses this situation by providing a casing spacer for a pair of joined pipes disposed within an outer casing which also provides a joint restraint for maintaining a sealed connection between the pipes.